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Earth history is punctuated by magmatic events marked by rapid emplacement of large volumes of mafic, ultramafic, and in some cases, silicic magma in an intraplate or incipient plate margin setting. Such events, termed Large Igneous Province (LIPs), include continental flood basalts, volcanic rifted margins, oceanic plateaus and ocean basin flood basalts (mainly of Mesozoic-Cenozoic age), feeder systems consisting of regional dyke swarms, sill provinces and layered intrusions (characteristic of Paleozoic and Proterozoic LIPs, which are typically more deeply eroded) and extensive tholeiite- komatiite± rhyolite sequences in the more deformed and dismembered Proterozoic to Archean record (e.g., greenstone belts).
The LIP plumbing system can be discussed in terms of the following levels in magma transport from mantle source to paleo-surface: 1) sub-lithospheric mantle source distribution and depth, 2) lithospheric entry points, 3) intra-lithospheric distribution of magma, and 4) surface magmatism. SUB-LITHOSPHERIC SOURCE DISTRIBUTION: Mantle source material (having elevated temperature, enriched in volatiles, and/or having fertile composition) has a sub-lithospheric distribution controlled by its origin (e.g. mantle plume, delamination, rifting). LITHOSPHERIC ENTRY POINTS: Above mantle upwellings (e.g. plumes), along active or failed rifts, along 'hot' sheets linked to lithospheric fracture, in 'thin spots' or at the edge of cratons. INTRA-LITHOSPHERIC DISTRIBUTION: Magma can be both vertically and laterally re-distributed within the lithosphere. Dyke swarms can transport magma laterally in the crust for distances of >2000 km and potentially feed distal volcanic or sill provinces (e.g. 2215 Ma Nipissing-Ungava event, Canada).
Very long distance lateral transport via sills is also possible (e.g. 180 Ma Ferrar sills, Antarctica). Mafic-ultramafic magmatism remaining at the base of the crust represents a magmatic underplate. Silicic melts can be generated by melting of fusible crustal rocks. Layered intrusions can have sill-like geometry, dyke-like geometry, or can be funnel-shaped, and the plumbing system for each is different. Funnel-shaped intrusions are centrally fed and may be the roots of volcanic systems (e.g. Rum, Skye etc.), and can also be aligned along (and linked) to a dyke or fracture zone. Major dyke-like layered intrusions (e.g. Great Dyke of Zimbabwe) are often part of regional dolerite dyke swarms. Layered intrusions of sill-like geometry are frequently emplaced at the supracrustal - basement interface, and can extend far from their feeders. SURFACE MAGMATISM: Flood basalts are typically fed from fissures and individual flows can travel more than 300 km. Point sources (i.e. shield volcanoes) also exist in some LIPs. Note that a substantial portion of the magmatic plumbing system may remain unconnected to the surface, i.e. may not feed surface lavas. Many LIPs are associated with carbonatites and some with kimberlites.
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